code: def update_delay(secs_since_start):
      # this sigmoid function reaches
      # - 0.1 after 11 minutes
      # - 0.5 after 15 minutes
      # - 1.0 after 23 minutes
      # in other words, the user will see very frequent updates
      # during the first 10 minutes
      sigmoid = 1.0 / (1.0 + math.exp(-0.01 * secs_since_start + 9.0))
      return MIN_UPDATE_DELAY + sigmoid * MAX_UPDATE_DELAY
  
file_path: metaflow/metaflow/mflog/__init__.py
imports: import math
  import time
  from .mflog import refine, set_should_persist
  from metaflow.util import to_unicode
  from metaflow.exception import MetaflowInternalError
label_desc: Use image node_id 2 for calling a global function with example usage: update_delay(secs_since_start) and returns: unknown